0000000000427823
AUTHOR
Czarnecka A.
Magnetic configuration effects on the Wendelstein 7-X stellarator
The two leading concepts for confining high-temperature fusion plasmas are the tokamak and the stellarator. Tokamaks are rotationally symmetric and use a large plasma current to achieve confinement, whereas stellarators are non-axisymmetric and employ three-dimensionally shaped magnetic field coils to twist the field and confine the plasma. As a result, the magnetic field of a stellarator needs to be carefully designed to minimize the collisional transport arising from poorly confined particle orbits, which would otherwise cause excessive power losses at high plasma temperatures. In addition, this type of transport leads to the appearance of a net toroidal plasma current, the so-called boot…
Confirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000
Fusion energy research has in the past 40 years focused primarily on the tokamak concept, but recent advances in plasma theory and computational power have led to renewed interest in stellarators. The largest and most sophisticated stellarator in the world, Wendelstein 7-X (W7-X), has just started operation, with the aim to show that the earlier weaknesses of this concept have been addressed successfully, and that the intrinsic advantages of the concept persist, also at plasma parameters approaching those of a future fusion power plant. Here we show the first physics results, obtained before plasma operation: that the carefully tailored topology of nested magnetic surfaces needed for good c…
Optimising the use of ICRF waves in JET hybrid plasmas for high fusion yield
In the recent JET experimental campaign, good progress was made in the development of high-performance plasma scenarios compatible with the ITER-like wall (ILW). This paper reports on the optimisation of the use of ion cyclotron resonance frequency (ICRF) waves for the hybrid scenario in combination with neutral beam injection. The hybrid scenario is a candidate for ITER long-pulse operation. The combined NBI+ICRF power was increased to 33 MW and the record JET ILW fusion yield, averaged over 100 ms, from 2.3x1016 neutrons/s to 2.9x1016 neutrons/s with respect to the previous 2014 JET ILW fusion record. Impurity control with ICRF waves was one of the key means for extending the duration of …